Personal computers (PCs), portable transmission devices, and other personal dedicated information processing devices perform text and graphics processing and the like via various input devices, such as a keyboard, a mouse, and a digitizer.
Input devices including only a keyboard and a mouse cannot deal with the extended uses of products, such as PCs, as input devices used for interfaces. Accordingly, there has been a need for an input device that is simpler than a conventional keyboard and mouse, that can reduce erroneous manipulations, that enables anyone to easily perform input operations, and that enables characters to be entered by a hand while it is being carried. In particular, a touch panel is known as an input device that is simple, that reduces erroneous manipulations, that enables anyone to perform input operations while carrying the input device, and that enables characters to be entered without another input device. The detection method, structure and performance thereof are well known.
Such touch panels include: resistive touch panels (screen) in which two sheets having respective resistance components that are disposed such that they are separated by a spacer and are brought into contact with each other by pressing have been combined with each other; capacitance touch panels in which current continuously flows along the surface of a panel and electrons flowing along liquid crystals are attracted to a contact point when a finger or conductor comes into contact with a screen, thereby achieving recognition; Surface Acoustic Wave (SAW) touch panels; optical (infrared) sensor touch panels; and electromagnetic touch panels.
Resistive touch panels are configured in a form in which a plurality of films (screens) is stacked on top of each other on liquid crystals. Resistive touch panels include a film disposed on the outermost side (a portion with which a hand or pen comes into contact) and made of material that is soft and robust to scratches, a film configured to mitigate impacts, and two transparent conductive films (thin transparent conductive substrates) configured to detect input, which are sequentially superimposed on top of each other.
Accordingly, resistive touch panels enable a screen to be touched with not only a finger but also a stylus pen (a touch pen) and almost all objects that can be held in a hand of a user, and are advantageous for successive handwriting inputs or small icon touches. Since the manufacturing costs of resistive touch panels are inexpensive because the principle thereof is simple, resistive touch panels are the most widely applied touch panels. Principal devices employing resistive touch panels include portable game consoles, such as the Nintendo DS, and mobile phones, such as Samsung Anycall Haptic phones and LG Cyon Cooky phones. These devices support handwriting input method-based games, or provide neat user interfaces.
Capacitive touch panels are based on a method using static electricity that is present in the human body. That is, current is made to continuously flow along liquid crystal glass by coating the liquid crystal glass with a conductive compound, and electrons flowing on the liquid crystal glass are attracted to a contact point when a finger comes into contact with a screen. Then, sensors present at corners of the touch screen detect the electrons and thus identify an input.
Accordingly, capacitive touch panels enable touch input to be performed even by slightly grazing a screen (which presents emotional sensations), and support multi-touch functionality (which enables the concurrent recognition of a plurality of contact points). Furthermore, since the liquid crystal glass coated with a dielectric (a conductive compound) is used, there is no concern about a reduction in image quality. Principal devices employing capacitive touch panels include most smart phones that have been recently released. The capacitance input method of capacitive touch panels is appropriate for the application of effective user interfaces to small screens, such as those of the above products. Recently, tablet PCs (such as the Samsung Galaxy Tab, the Apple iPad, etc.) equipped with screens larger than those of mobile phones have attracted attention. Most of these tablet PCs employ capacitance touch screens rather than resistive touch screens.
FIG. 1 is a plan view showing a conventional capacitive touch panel.
As shown in FIG. 1, the conventional capacitive touch panel includes a plurality of bottom transparent electrodes 110, a plurality of top transparent electrodes 120, and electrode terminals 130 and 140 connected to the respective electrodes. It will be apparent that the conventional capacitive touch panel may include components, such as a cover made of tempered glass or reinforced plastic and an optical transparent adhesive, in addition to the components shown in FIG. 1. Since these components are apparent to those skilled in the art, detailed descriptions thereof are omitted.
The plurality of bottom transparent electrodes 110 may be each formed linearly in a first direction, for example, a lateral direction (an x axis direction), and may be formed on a lower transparent substrate (not shown).
In this case, the plurality of bottom transparent electrodes 110 may be disposed at predetermined gaps in a second direction, for example, a vertical direction (a y axis direction).
The plurality of top transparent electrodes 120 is formed in a direction perpendicular to the plurality of bottom transparent electrodes 110. That is, the plurality of top transparent electrodes 120 is formed in the second direction perpendicular to the first direction.
In this case, the plurality of top transparent electrodes 120 may be formed on an upper transparent substrate (not shown).
In the conventional capacitive touch panel configured as described above, a mutual capacitance value is generated between the bottom transparent electrode 110 and the top transparent electrode 120 at each point where the electrodes intersect each other. When the human body comes into contact with or approaches the point, part of the mutual capacitance value generated at the intersection point is transferred to the human body due to the virtual ground phenomenon of the human body. In this case, the mutual capacitance value is reduced at the intersection point, and the recognition of contact with the human body and coordinate calculation are performed based on the change in mutual capacitance.
In the conventional capacitive touch panel, the bottom transparent electrodes 110 are arranged at gaps of about 5 mm based on a diameter ranging from 5 to 6 mm, which corresponds to a human body contact area. The bottom transparent electrodes 110 may be arranged at gaps of a maximum of 6.5 mm based on the material and thickness of the cover.
However, when the number of electrodes or electrode terminals available in the structure of the conventional capacitive touch panel is insufficient, the electrodes are arranged at wider gaps, for example, gaps of 10 mm. In this case, a problem arises in that it becomes difficult to identify contact with the human body, with the result that it becomes difficult to calculate accurate coordinates. That is, the electrode structure of the conventional capacitive touch panel has a problem in that it cannot guarantee coordinate linearity.
Therefore, there is a need for a touch panel that can guarantee coordinate linearity even when the number of available electrodes is insufficient and thus can provide the accurate coordinate values of a touched location.